Motor fuel containing diimine additives

ABSTRACT

CERTAIN DIIMINE COMPOUNDS, CHARACTERIZED AS THE 1,3DIIMINO-2-HYDROXYPROPANES, ARE EFFECTIVE FOR IMPROVING THE ANTIKNOCK PERFORMANCE AND IGNITABILITY OF MOTOR FUELS EMPLOYED IN HIGH COMPRESSION, SPARK-IGNITION-TYPE ENGINES.

United States" Patent Oflibe 3,685,976 Patented Aug. 22, 1972 MOTOR FUEL CONTAINING DlIMlNE ADDITIVE Jan H. Vis, Hengelo, Netherlands, and Wallace R. Loder,

In, North Olmsted, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio No Drawing. Filed May 24, 1971, Ser. No. 146,541

Int. Cl. C101 1/22 U.S. Cl. 44-69 Claims ABSTRACT OF THE DISCLOSURE Certain diimine compounds, characterized as the 1,3- diimino-2-hydroxypropanes, are effective for improving the antiknock performance and ignitability of motor fuels employed in high compression, spark-ignition-type engines.

This invention relates to an improved liquid motor fuel additive composition and more particularly to a motor fuel composition for use in high compression, spark-ignition engines containing minor amounts of diimine compounds. The motor fuel additives contemplated to be within the scope of this invention may be characterized as the 1,3-diimino-Z-hydroxypropanes corresponding to the following general formula:

wherein R and R may be the same or difierent and wherein R and R may be an alkyl or a substituted alkyl group containing from about 3 to carbon atoms, a cycloalkyl or a substituted cycloalkyl group containing from about 4 to 10 carbon atoms, or an aromatic or a substituted aromatic hydrocarbon group, containing from about 6 to 10 carbon atoms. The substituent groups on the foregoing R and R radicals may be alkyl, hydroxy, methoxy, carbonyl, carboxyl, halogen, nitro or amine groups. The R R R and R radicals may be hydrogens or methyl groups.

It is well known that during the operation of an initially clean internal combustion engine, deposits form progressively and accumulate on the surfaces within the combustion zone, and as the operation continues, the amount of the deposits reaches a level after which there is no appreciable further increase in the amount of the deposits. The engine is then regarded as having reached deposit equilibrium, and old deposits flake off as fast as new deposits form.

The deposit problem is aggravated when tetraethyl lead is contained in the fuel because the deposits are then no longer essentially carbonaceous, but comprise appreciable quantities of lead and lead compounds generally mixed with the carbonaceous material. The fact that this deposit is partially metallic in character is thought to give it a catalytic activity which modifies the action of the deposit in affecting engine operation.

These deposits have a number of adverse effects upon engine operation. One adverse effect of the deposits is manifested by an increase in the octane requirement of the engine. This requirement for a fuel of higher octane number as the engine becomes progressively dirtier, persists until the deposits reach equilibrium, and is known as octane requirement increase (0R1).

In addition to the adverse effects of combustion chamber deposits, approximately one-third of all cars on the highways sulfer from subnormal ignition. Some of these ignition difliculties arise from weak batteries in starting, worn points, oil and water-soaked electrical wiring known as harness, frayed or broken harness, weak coils, etc. All of these deficiencies tend to diminish the voltage delivered to the spark plugs.

The spark plugs themselves may contribute to ignition difiiculties as well. With use, the electrodes erode, increasing the breakdown voltage of the gap. The lead from the binding post to the center electrode may break, requiring additional voltage to leap across that break as well as across the gap. The ceramic surfaces of the spark plug become fouled with deposits which act as short circuits and drain the voltage from the electrodes.

The resulting situation is that both use and abuse steadily raise the voltage required to jump the spark across the proper gap, while at the same time the voltage available at the gap steadily declines as the car ages. At some point in this process of deterioration, less voltage will be delivered to the electrodes than is required, and the spark will not jump the gap. The result of this deteriorating situation is diflicult starting, misfiring or late firing, loss of power, especially during acceleration or hill climbing, and increased air pollution.

It is therefore an object of this invention to provide a motor fuel formulation that will alleviate the above problems that are common to the majority of sparkignition-type automotive vehicles that are presently on the road. The additives of this invention are believed to promote ionization of the fuel thus improving conductivity of the gases contained in the spark plug gap, and they are also combustion chamber deposit modifiers. When added to motor fuels in minor amounts, the additives of this invention are effective in lowering the octane requirement, in minimizing the octane requirement increase and generally improving the antiknock performance of a fuel in a spark-ignition-type engine. The diimine additives of this invention are believed to be metal complexing agents, and it is postulated that when they are added to motor fuels containing organolead antiknock agents they interact with some of the lead during the combustion process and further improve the antiknock performance of the lead, thereby also functioning as lead appreciators.

U.S. Patent No. 3,248,410 issued Apr. 26-, 1966 discloses the preparation of a monomeric polymerizable heavy metal chelate complex of the diimine structure shown herein above, and its use in modifying the burning rate properties of solid polymeric propellant binders. However, the use of these diimine compounds for improving octane performance and ignitability of motor fuels according to the present invention has heretofore not been proposed.

In accordance with this invention, diimines of the above designation may be added advantageously to leaded or unleaded motor fuels in concentrations ranging from about parts to 1000 parts per million based on the fuel. Although improved performance may also be obtained at higher concentrations, the solubility limits in the I N,N'-disalicylidene-Z-hydroxy-1,3-propyldiimine N,N'-dibenzylidene-Z-hydroxy-1,3-propyldiimine H30 fl N,N'-dihexahydrobenzylidene-2-hydroxy-1,3-

propyldiimine N,N -disalicylindene-Z-hydroxy-1,3-dimethyl-l,3-

propyldiimine When an organolead antiknock agent such as tetraethyl lead is present in the fuel, the fuel may also contain a lead scavenging agent such as a volatile alkyl halide or a mixture of volatile alkyl halides such as ethylene dichloride and/or ethylene dibromide as is well-known in the art. These halides are usually present as 1 theory of ethylene dichloride and theory of ethylene dibromide (the so-called motor mix) or 1 theory of ethylene dibromide (the so-called aviation mix). By theory is meant the stoichiometric amount of the ethylene dihalide for combination with all of the lead as lead halide.

The base gasoline stock useful as fuel in this invention can comprise a mixture of hydrocarbons boiling in the gasoline range and can be either a straight-run gasoline or a gasoline obtained from a conventional cracking process, or mixtures thereof. The base gasoline may also contain components obtained from various other refinery processes, such as alkylation, isomerization, hydrogenation, polymerization, catalytic reforming, or combinations of two or more of such processes.

It is intended that the motor fuel of this invention may also include other known additives for commercial fuels, such as detergents, oxidation inhibitors, gum inhibitors, deicers, dyes, solvent oils and the like.

To determine the effect of diimines on the octane rating of leaded and unleaded motor fuels, blended fuels were 4 evaluated in the standard ASTM (research) and ASTM (motor) octane test procedures. In these tests additive compositions, additive and tetraethyl lead concentrations were varied and the results were compared with tertiary butyl acetate at its most eifective concentration. The elfect of the additives on the octane rating of motor fuels is demonstrated by the examples given in Tables II, III and IV.

The physical and chemical properties of the base fuel employed in the octane test program were as follows:

TABLE I Distillation: F. Initial B.P. 94

Percent recovered 98 Percent residue 1 Percent loss 1 Gravity, API 60.2 RVP 8.1 Octane ASTM research 93. Octane ASTM motor 83.6 TEL, cc./gal 0 Composition: Volume percent Lt. isocrackate 24 Lt. catalytic distillate 19 Total catalytic reformate 35 Alkylate 18 Natural gasoline 4 TABLE II Increase in Tetraoctane No. ethyl, over base Example C0nc., lead. fuel Without No. Additive moles/gal. cc/.gal. additive ASTM research octane rating N,N-disal. hyd. 0. 0606 0 2.6 2 N,Ndipont. h d. 0. 0174 0 1. 3 3 Tert butyl acetate 0.0606 0 0.!) 4.- N,N-disal. hyd... 0.0606 1 4.1 5.- N,N-dipent hy 0.0174 1 3.7 6 Tert. butyl acetate 0. 0606 1 3. 4 7.. N,N-disal.hyd 0.0606 3 1.3 8.- N,N'-dipent. hyd 0.0696 3 1.1 9 Tert. butyl acetate 0 0696 3 1.8

ASTM motor octane rating 10 N,N-disa1. hyd 0.0606 0 1.0 0.0174 0 1.4 0.0606 0 -0.2 13 N,N-disa1. 0.0696 1 1.0 14 N,N-dipent. hyd 0.0174 1 0.4 15 Tert. butyl acetate 0.0690 1 0.1 16 N,N-disal.hyd 0.0696 3 1.3 17 Tert. butyl acetate 0. 0696 3 1.0

1 N ,N-disa1. hyd.=N,N-disalicylidene-Z-hydroxy-l,3-propy1diimine. 2 N,N-dipent. hyd. =N,N-di(2-pentylidene4-one)-2-hydroxy-1,3'propyldiirnine.

Examples 1 to 17 shown in Table II indicate that at zero concentration of tetraethyl lead the diimine compounds show antiknock behavior by themselves, and a greater octane response is indicated for these additives than for an equivalent concentration of tertiary butyl acetate. The increase in octane response resulting from the diimine additive is not as great with increasing concentrations of tetraethyl lead, however, the increase in octane ratings of leaded fuel attributable to the diimine additive is still appreciable.

The effect of diimine compounds on the control of octane requirement increase of a fuel was measured in a -hour single cylinder test. The tests were conducted in a Waukesha CPR-48 octane engine coupled to a variable speed dynamometer so as to provide cycling capability. The test fuel employed in these tests was .the same as that shown in Table I. The test cycle conditions were as follows: I

CYCLING SCHEDULE Cycle duration, seconds 0 Cycle speed, r.p.rn... Throttle setting Test conditions:

Length of run-100 hours Ignition timing6 BTDC Compression ratio, nominal-9: 00: 1 Coolant temperature220 F. Oil temperaturel50 F. Inlet air temperature100 F. Spark plug gap-0.020

engine has a lower octane requirement after the additive fuel has been run than before. This effect is demonstrated by Examples 24 to 34 given in Table IV. It is also seen that the higher the additive concentration, the stronger the aftereifect, both in length and intensity.

To determine the effect of the diimine additives on the ignitability of motor fuel, acceleration tests were carried out in a 302 cubic inch 1970 Ford V-8 engine. The test employed measured the ability of a gasoline to deliver power under a variety of conditions ranging from those producing severe misfiring to those producing no misfiring. Critical performance occurred during acceleration at wide open throttle. The means for inducing misfire consisted of reducing the voltage available at the primary winding of the spark coil to a substandard level. Under these conditions, the power output of the engine was reduced below that level normally observed at full ignition voltage. The increase in power output of the additive fuel compared with the base fuel in terms of horsepower was employed as a measure of the ability of the additive to improve the ignitability of the fuel.

In the tests carried out in the instant invention, the engine was coupled to an Eaton Dynamatic Universal dynamometer. The engine was equipped with a finely adjustable ignition voltage supply and a digital voltmeter. In conducting these tests, the engine power output was adjusted to a target level using the base fuel, and tests were then run between power levels of 65 percent and TABLE IV [Additivez N ,Ndisaileylidene2-hydroxy-l,3-propyldiimine] Minutes Duration of 4 8 16 32 Cone. of After- Example Tetraethyl addit, effect, Increase in octane number of reference No. lead, ccJgal. moles/gal. min. fuel during 1 min. Afterefiect ASTM research test conditions AS'IM motor test conditions The results of measurements of octane requirement increase (ORI) of the fuel are summarized in Table III. The data show that ORI of the engine is reduced considerably with fuels containing the diimine additives.

Another effect that is characteristic of fuels containing the diimine additive of this invention is aftereifect. Under normal circumstances, the reference fuel octane response is the same before and after running the additive fuel in the engine. The time required for the reference fuel to return to previous octane level after running the additive fuel is approximately 2 to 5 minutes. This time is considerably longer for fuels containing the diimine additives so that the reference fuel has a higher octane number after the additive fuel has been run in the engine than before. Expressing this effect in another way, the

TABLE III.-100 HOUR TEST l N,N-disalieylidene-2-hydroxy-1,3-propyldiimine. 2 N ,Ndibenzylidene-Z-hydroxy-l,3-propyldiimine.

100 percent of full power, as determined with the base fuel. The additive-containing fuels were evaluated in a series of tests with base fuels interspersed as reference points. The engine test cycle involved acceleration and idling under the following conditions:

Time, Phase N, r.p.m. T, load H.P. seconds 1 Idle 1200.-. 4.5 60 2. Accel. to z r.p. Variable 6 3 Cruise 2000-.. 48 60 The cycle was run under the following conditions:

Water jacket outlet temperature, F.1'65:5 Oil sump temperatureEquilibriurn Carburetor adjustmentsFactory specification Inlet air, F.

TorqueXr.p.m.

Termmal Dynamometer constant Data produced from the above tests were fed into a computer to obtain a regression equation based on a full quadratic model.

The base fuel used in the acceleration tests had the specifications shown in Table V.

TABLE V Distillation: F.

IBP 88 125 50% 214 90% 331 Percent recovered 98 Percent residue 1.0

Percent loss 1.0 Gravity, API 61.3 RVP 9.7 Octane ASTM (research) 100.4 Octane ASTM (motor) 92.7 TEL, cc./gal. 2.98

Composition: Volume percent Lt. isocrackate 22 Lt. catalytic distillate 18 Catalytic reformate 33 Alkylate Natural gas 4 N-butane 3 SEB-78 0.25

The eflect of the various imine compounds on power delivery of the fuel is shown by the examples given in Table VI.

TABLE VI Fractional power level Example No. p.p.m. additive Horsepower Additive: N,N-disallcylidene-2-hydroxy-1,3-propyldiimine Additive: N ,N-dihexahydrobenzylidene-2-hydroxy-1,3-propyldiimine Additive: N,N-dibenzylidene-2-hydr0xy-i,3-propyldiimine We claim:

1. A motor fuel composition for internal combustion engines containing from about parts to 1000 parts per million based on the motor fuel of a diimine compound having the formula:

wherein R and R may be the same or different and wherein R and R may be selected from the group consisting of an alkyl or a substituted alkyl group containing from about 3 to 10 carbon atoms, a cycloalkyl or a substituted cycloalkyl group containing from about 4 to 10 carbon atoms, and an aromatic or a substituted aromatic group containing from about 6 to 10 carbon atoms, and wherein the substituting groups on said foregoing R and R radicals may be alkyl, hydroxy, methoxy, carbonyl, carboxyl, halogen, nitro or amine groups, and R R R and R may be hydrogens or methyl groups.

2. The motor fuel composition of claim 1 wherein the fuel contains up to 6 cc. of tetraalkyl lead per gallon and a halide scavenging agent.

3. The motor fuel composition of claim 1 wherein the diimine compound is a member selected from the group consisting of N,N-disalicylidene-Z-hydroxy-1,3-propyldiimine, N,N-dibenzylidene 2 hydroxy-1,3-propylidiimine, N,N'-di(2-pentylidene-4-one) 2 hydroxy-1,3- propyldiimine and N,N-dihexahydrobenzylidene-Z-hydroxy-1,3-propyldiimine.

4. The motor fuel composition of claim 3 wherein the diimine compound is N,N-disalicylidene-Z-hydroxy-1,3- propyldiimine.

5. The motor fuel composition of claim 3 wherein the diimine compound is N,N'-dibenzylidene-Z-hydroxy-1,3- propyldiimine.

References Cited UNITED STATES PATENTS 2,533,205 12/1950 Chenicek 4473 2,626,208 1/1953 Brown 44--73 3,034,876 5/1962 Gee et a1. 44-73 3,248,410 4/1966 Berenbaum 260439 R PATRICK P. GARVIN, Primary Examiner Y. H. SMITH, Assistant Examiner US. 01. x.R. 44 73 

